DNA vaccination for treatment of autoimmune disease

ABSTRACT

A pro-inflammatory T cell response is specifically suppressed by the injection into a recipient of DNA encoding an autoantigen associated with autoimmune disease. The recipient may be further treating by co-vaccination with a DNA encoding a Th2 cytokine, particularly encoding IL4. In response to the vaccination, the proliferation of autoantigen-reactive T cells and the secretion of Th1 cytokines, including IL-2, IFN-γ and IL-15, are reduced.

CROSS-REFERENCES

This application claims priority to earlier filed International PatentApplication Ser. No. PCT/US00/06233, filed Mar. 10, 2000 whichapplication claims priority to U.S. patent application Ser. No.09/267,590 filed Mar. 12, 1999, both of which applications areincorporated herein by reference in their entirety.

INTRODUCTION

The complexity of the immune system has been a daunting barrier to anunderstanding of immune system dysfunction. In recent years, thetechniques of molecular biology have provided insight into themechanisms and components that underlie immunity. To a large extent, thestory of immunity is the story of lymphocytes. Lymphocytes possess anextremely complex and subtle system for interacting with each other,with antigen-presenting cells, and with foreign antigens and cells.

Modulation of the immune response varies with the specific factorsproduced, and the receptors present on the responding cell. The pathwaysfor down-regulating responses are as important as those required foractivation. T cell tolerance is one well-known mechanism for preventingan immune response to a particular antigen. Other mechanisms, such assecretion of suppressive cytokines, are also known.

A common feature in a number of diseases and inflammatory conditions isthe involvement of pro-inflammatory CD4⁺ T cells. These T cells areresponsible for the release of inflammatory, Th1 type cytokines.Cytokines characterized as Th1 type include interleukin 2 (IL-2),γ-interferon, TNFα and IL-12. Such pro-inflammatory cytokines act tostimulate the immune response, in many cases resulting in thedestruction of autologous tissue. Cytokines associated with suppressionof T cell response are the Th2 type, and include IL-10, IL-4 and TGF-β.It has been found that Th1 and Th2 type T cells may use the identicalantigen receptor in response to an immunogen; in the former producing astimulatory response and in the latter a suppressive response.

Cytokines play a critical role in the development and recovery fromautoimmune diseases. Th1 cytokines such as interleukin 12 (IL-12) andinterferon gamma (IFNγ) have been found in the central nervous system(CNS) of multiple sclerosis (MS) patients as well as in animals with EAE(Issazadeh et al. (1995). J Neuroimmunol 61:205–12). Th2 cytokines suchas IL-4, IL-5 and IL-10 have been found to be elevated either duringremission of MS or EAE (Waisman et al. (1997) Immunointervention inautoimmunity by Th1/Th2 regulation, L. Adorini, ed. (Austin, Tex.: R.G.Landes Co.), pp. 129–50). Previous studies have shown that systemicadministration of IL4 as well as local CNS administration of IFNγ canreduce the severity of EAE (Racke et al. (1994) J Exp Med 180:1961–6;Voorthuis et al. (1990) Clin Exp Immunol 81:183–8). Furthermore, theaddition of IL-4 to naive T cells can result in the development of Th2type cells, whereas the addition of IL-12 can result in the developmentof Th1 type cells (Macatonia et al. (1993) Int Immunol 5:1119–28).

DNA vaccination is effective in protecting experimental animals againstinfectious pathogens and cancer, and recently has been used to preventautoimmune disease (Waisman et al. (1996) Nat Med 2, 899–905).Experimental autoimmune encephalomyelitis (EAE), a prototypic animalmodel of T cell autoimmunity, reflects many of the clinical andpathologic features of the human disease, multiple sclerosis.

In order to modify immune responses to DNA vaccines, DNA co-vaccinationhas been performed with cytokine genes, along with the genes for certainpathogens. Examples include DNA immunization with hepatitis B virusantigens and IL-2 DNA which enhanced TH1 responses, HIV antigens withIL-12 DNA which enhanced cytotoxic T cell activity, and influenzaantigens with IL-6 DNA which enhanced anti-viral activity (see, forexample, Chow et al. (1998) J Immunol 160(3):1320–9).

Vaccination of mice with naked DNA that encodes the predominant T cellreceptor (TCR) β chain that is rearranged in myelin basic protein (MBP)reactive T cells, has been shown to protect mice from EAE. Suchimmunization induced a pattern of Th2 cytokine production by myelinreactive T cells, creating a suppressive environment blockingautoimmunity: T cells reacting to the myelin autoantigen deviated froman aggressive T helper 1 (Th1) type to a suppressive Th2 type.

Further development of treatment that specifically inhibits T cellactivation would be of great medical benefit.

Relevant Literature

Waisman et al. (1996) Nat. Med. 2:899–905 and) Offner et al. (1998) J.Immunol. 161:2178–2186 describe the use of DNA vaccination to preventexperimental autoimmune encehalomyelitis (EAE). The injection of DNA topromote vaccination against microbes and tumors is discussed in Cohen etal. (1997) Hosp. Pract. 32:169–171; Syrengelas, et al. (1996) Nat. Med.2:1038–1041; Ulmer et al. (1996) Curr Opin Immunol. 8:531–536.; Pardollet al. (1995) Immunity 3:165–169; Davis et al. (1993) Hum. Mol. Genet.2:1847–1851; Ulmer et al. (1993) Science 259:1745–1749; and Tang et al.(1992) Nature 356:152–154. Genetic immunization has demonstratedinduction of both a specific humoral but also a more broadly reactingcellular immune response in animal models of cancer, mycoplasma, TB,malaria, and many virus infections, including influenza and HIV. See,for example, Mor et al. (1995) J Immunol 155:2039–46; Xu and Liew (1995)Immunology 84:173–6; and Davis et al. (1994) Vaccine 12:1503–9.

Susceptibility to multiple sclerosis (MS) has been associated withcertain MHC Class II genes, Oksenberg and Steinman (1990) CurrentOpinion in Immunology 2:619–621. At the cellular level, oligoclonalityof T-cells has been described in the cerebrospinal fluid (CSF) of MSpatients, Lee et al., Ann. Neurol. 29:33–40 (1991).

CNS antigens, including myelin proteins, studied in the context of MSare discussed in de Rosbo et al., J. Autoimmunity 11:287–299 (1998).Enhancers of the immune response to DNA vaccines include unmethylatedCpG dinucleotides, Krieg et al. (1998) Trends Microbiol. 6:23–27, andfused pathogen-derived sequences, King et al. (1998) Nat. Med.4:1281–1286.

SUMMARY OF THE INVENTION

Methods are provided for the suppression of pro-inflammatory T cellresponses in autoimmune disease. A mammalian host is vaccinated with aDNA expression vector encoding an autoantigen fragment. In response tothe vaccination, pathogenic T cell proliferation is inhibited andproduction of Th1 cytokines, including IL-2, IL-10, IFN-γ and IL-15 isreduced. In one embodiment of the invention, a nucleic acid encoding aTh2 cytokine is co-administered with the autoantigen coding sequence.The use of IL-4 coding sequences is of particular interest. Suppressivevaccination diminishes T cell pro-inflammatory responses in a specific,targeted manner. Conditions that benefit from this treatment includeautoimmune diseases, tissue transplantation and other diseasesassociated with inflammation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Anti-SCH IgG (A) and anti-PLP139–151 (B) antibody titers inSJL/J mice after DNA immunization with the PLP minigene.

FIG. 2. Lymph node cell proliferative responses to PLP139–151 (squares)and the control peptide PLP178–191 (triangles) for animals injected withDNA coding for PLP139–151 (A) or control vector, pTARGET (B).

FIG. 3. (A) Levels of γ-interferon (striped bars) or IL-2 (dotted bars)in animals vaccinated with plasmid DNA coding for PLP139–151 or vectoralone (pTARGET). (B) Cytokine mRNA detection and analysis by 5%polyacrylamide gel electrophoresis.

FIG. 4. Surface expression of B7.1, B7.2, and I-A^(s) of spleen cellsafter incubation with DNA. Numbers in quadrants refer to the percentageof cells in the monocyte gate (A) or the lymphocyte gate (B) as definedby forward and side scatter.

FIG. 5. Incidence of diabetes in DNA vaccinated NOD mice. Female NODmice were injected with either empty plasmid DNA (▴), plasmid encodinginsulin B (9–23) (▪), or plasmid encoding insulin A (7–21) (♦); onegroup was left untreated (●).

FIG. 6. Quantitative PCR measurement of cytokine expression bypancreatic lymph node cells from vaccinated NOD mice cultured with 10μg/ml insulin B (9–23) peptide. PcDNA control vaccinated levels (solidbars) were used as a standard against which the insB-PcDNA vaccinatedvalues (hatched bars) were compared.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

The subject methods provide a means for therapeutic treatment andinvestigation of inflammation, through the suppression of pathogenicantigen-specific T-cell responses. A DNA expression cassette is injectedinto host tissue, for example muscle or skin. The vector comprises a DNAsequence encoding at least a portion of an autoantigen. The vaccinationmay also include DNA sequences encoding a Th2 cytokine, e.g. IL-4. Inresponse to this vaccination, a suppressive response is evoked.Antigen-specific T cell proliferation is inhibited and Th1 cytokineproduction is reduced.

Without limiting the scope of the invention, it is believed that themethods described herein are a novel method of protective immunity,which combines the effects of DNA vaccination and local gene delivery.After DNA vaccination with a autoantigen epitope alone, T cells areanergic. This may be in part due to the biological effects of DNA motifslike unmethylated CpG dinucleotides in particular base contexts (CpG-Smotifs) (Krieg et al. (1998) Trends in Microbiol. 6:23–27). The additionof IL4 as a DNA co-vaccine rescues the anergy imposed by the autoantigenDNA vaccine, and drives the response to a Th2 phenotype. STAT6 isactivated in draining lymph node cells by the IL4 DNA vaccine. It isbelieved that IL4 is produced from the DNA vaccine administered and thatit interacts with IL4 receptor on lymph node cells, which in turn causesthe activation of STAT6 downstream of the receptor. Immunization againstthe antigens that trigger those autoimmune diseases caused by Th1autoreactive cells, diseases such as multiple sclerosis, juvenilediabetes and rheumatoid arthritis, would be conditions whereco-vaccination with DNA encoding IL-4 might prove beneficial

Autoantigens, as used herein, are endogenous proteins or fragmentsthereof that elicit a pathogenic immune response. Of particular interestare autoantigens that induce a T cell mediated inflammatory pathogenicresponse. Suppressive vaccination with the relevant target autoantigenfinds use in the treatment of autoimmune diseases characterized by theinvolvement of pro-inflammatory T cells, such as multiple sclerosis,experimental autoimmune encephalitis, rheumatoid arthritis and insulindependent diabetes mellitus. Animal models, particularly small mammals,e.g. murine, lagomorpha, etc. are of interest for experimentalinvestigations.

The subject methods of suppressive immunization are used forprophylactic or therapeutic purposes. Use used herein, the term“treating” is used to refer to both prevention of disease, and treatmentof pre-existing conditions. The prevention of autoimmune diseaseinvolving the vaccine autoantigen (VA), is accomplished byadministration of the vaccine prior to development of overt disease. Thetreatment of ongoing disease, where the suppressive vaccinationstabilizes or improves the clinical symptoms of the patient, is ofparticular interest. Such treatment is desirably performed prior tocomplete loss of function in the affected tissues.

Autoantigens known to be associated with disease include myelin proteinswith demyelinating diseases, e.g. multiple sclerosis and experimentalautoimmune myelitis; collagens and rheumatoid arthritis; insulin,proinsulin, glutamic acid decarboxylase 65 (GAD65); islet cell antigen(ICA512; ICA12) with insulin dependent diabetes. An association of GADepitopes with diabetes is described in a number of publications,including U.S. Pat. No. 5,212,447; and European patent application no.94.927940.0. An association of insulin epitopes with autoimmuneinsulitis is described in Griffin et al. (1995) Am. J. Pathol.147:845–857. Rudy et al. (1995) Mol. Med. 1:625–633 disclose an epitopethat is similar in GAD and proinsulin.

The protein components of myelin proteins, including myelin basicprotein (MBP), proteolipid protein (PLP), myelin-associated glycoprotein(MAG) and myelin oligodendrocyte glycoprotein (MOG), are of particularinterest for use as immunogens of the invention. The suppression of Tcell responsiveness to these antigens is used to prevent or treatdemyelinating diseases.

In one embodiment of the invention, the vaccine autoantigen isproteolipid. For convenience, a reference sequence of human PLP isprovided as SEQ ID NO:1; and human myelin basic protein as SEQ ID NO:3.Proteolipid is a major constituent of myelin, and is known to beinvolved in demyelinating diseases (see, for example Greer et al. (1992)J. Immunol. 149:783–788 and Nicholson (1997) Proc. Natl. Acad. Sci. USA94:9279–9284).

The integral membrane protein PLP is a dominant autoantigen of myelin.Determinants of PLP antigenicity have been identified in several mousestrains, and include residues 139–151 (Tuohy et al. (1989) J. Immunol.142:1523–1527), 103–116 (Tuohy et al. (1988) J. Immunol. 141:1126–1130],215–232 (Endoh et al. (1990) Int. Arch. Allergy Appl. Immunol.92:433–438), 43–64 (Whitham et al. (1991) J. Immunol. 147:3803–3808) and178–191 (Greer, et al. (1992) J. Immunol. 149:783–788). Immunizationwith native PLP or with synthetic peptides corresponding to PLP epitopesinduces EAE. Analogues of PLP peptides generated by amino acidsubstitution can prevent EAE induction and progression (Kuchroo et al.(1994) J. Immunol. 153:3326–3336, Nicholson et al. (1997) Proc. Natl.Acad. Sci. USA 94:9279–9284).

MBP is an extrinsic myelin protein that has been studied extensively. Atleast 26 MBP epitopes have been reported (Meinl et al. (1993) J. Clin.Invest. 92:2633–2643). Of particular interest for use in the presentinvention are residues 1–11, 59–76 and 87–99. Analogues of MBP peptidesgenerated by truncation have been shown to reverse EAE (Karin et al.(1998) J. Immunol. 160:5188–5194). DNA encoding polypeptide fragmentsmay comprise coding sequences for immunogenic epitopes, e.g. myelinbasic protein p84–102, more particularly myelin basic protein p87–99,(SEQ ID NO:11) VHFFKNIVTPRTP (p87–99), or even the truncated 7-merpeptide (SEQ ID NO:12) FKNIVTP. The sequences of myelin basic proteinexon 2, including the immunodominant epitope bordered by amino acids59–85, are also of interest. For examples, see Sakai et al. (1988) JNeuroimmunol 19:21–32; Baxevanis et al (1989) J Neuroimmunol 22:23–30;Ota et al (1990) Nature 346:183–187; Martin et al (1992) J Immunol.148:1350–1366, Valli et al (1993) J Clin Inv 91:616. The immunodominantMBP(84–102) peptide has been found to bind with high affinity toDRB1*1501 and DRB5*0101 molecules of the disease-associated DR2haplotype. Overlapping but distinct peptide segments were important forbinding to these molecules; hydrophobic residues (Val189 and Phe92) inthe MBP (88–95) segment for peptide binding to DRB1*1501 molecules;hydrophobic and charged residues (Phe92, Lys93) in the MBP (89–101/102)sequence contributed to DRB5*0101 binding.

The transmembrane glycoprotein MOG is a minor component of myelin thathas been shown to induce EAE. Immunodominant MOG epitopes that have beenidentified in several mouse strains include residues 1–22, 35–55, 64–96(deRosbo et al. (1998) J. Autoimmunity 11:287–299, deRosbo et al. (1995)Eur J Immunol. 25:985–993) and 41–60 (Leadbetter et al. (1998) J Immunol161:504–512).

For the treatment of diabetes, immunogens of interest include IA-2;IA-2beta; GAD; insulin; proinsulin; HSP; glima 38; ICA69; and p52. Forexample, insulin (which sequence is publicly available, for example fromSures et al. (1980) Science 208:57–59; Bell et al. (1979) Nature282:525–527; and Bell et al. (1980) Nature 284:26–32) has been found tohave immunodominant epitopes in the B chain, e.g. residues 9–23; as wellas in the pre-proinsulin leader sequence. Other autoantigens associatedwith diabetes include glutamic acid decarboxylase 65 (GAD65), e.g.residues 206–220; 221–235, 286–300; 456–470; and peptides includingresidues p247, p509; p524 (Kauffman et al. (1993) Nature 366:69–72).

A DNA expression cassette encoding at least a portion of an autoantigen,usually as part of a vector, is introduced into tissue of the vaccinerecipient. The minigene is expressed in the tissue, and the encodedpolypeptide acts as an immunogen, or antigen. The autoantigen sequencemay be from any mammalian or avian species, e.g. primate sp.,particularly humans; rodents, including mice, rats and hamsters;rabbits; equines, bovines, canines, felines; etc. Of particular interestare the human and mouse autoantigen segments. Generally, the sequencewill have the same species of origin as the animal host, preferably itwill be autologous

The subject DNA expression cassette will comprise most or all of thesequence encoding an autoantigen fragment, as defined by Kabat et al,supra. The coding sequence may be truncated at the 5′ or 3′ terminus andmay be a fragment of the complete polypeptide sequence. In oneembodiment of the invention, the sequence encodes a peptide fragmentthat is known to be presented to pathogenic T cells, for examplepeptides presented by Class II MHC molecules of the host. Such peptideshave been described in the literature, and are typically of about 8 toabout 30 amino acids in length.

The vaccine may be formulated with one or a cocktail of autoantigensequences. While it has been found that a single sequence is capable ofsuppressing a response to multiple epitopes, it may be desirable in somecases to include multiple sequences, where each encodes a differentepitope. For example, see Leadbetter et al. (1998) J. Immunol.161:504–512. A formulation comprised of multiple coding sequences ofdistinct PLP epitopes may be used to induce a more potent and/orsustained suppressive response. By specifically targeting multipleautoreactive T cell populations, such a formulation may slow or preventthe development of autoantigen resistance. The use of PLP sequences incombination with other myelin protein epitopes may effectively suppressthe repertoire of myelin-reactive T cells. Similar autoantigencombinations to suppress autoimmune response, e.g., glutamic aciddecarboxylase (GAD) and pancreatic islet cell autoantigen for thetreatment of insulin dependent diabetes, are contemplated.

In addition to the specific epitopes and polypeptides of autoantigens,the immune response may be enhanced by the inclusion of CpG sequences,as described by Krieg et al. (1998) Trends Microbiol. 6:23–27, andhelper sequence, King et al. (1998) Nat. Med. 4:1281–1286. Biologicaleffects of DNA motifs like unmethylated CpG dinucleotides in particularbase contexts (CpG-S motifs) may modulate innate immune responses wheninjected to animals. Low numbers of CpG motifs, or the presence ofimperfect motifs, may act in the development of anergy by immunizationwith autoantigens.

The polypeptide coding sequence, which may be autoantigen or cytokine,sequences are inserted into an appropriate expression cassette. Theexpression construct is prepared in conventional ways. The cassette willhave the appropriate transcriptional and translational regulatorysequences for expression of the sequence in the vaccine recipient cells.The cassette will generally be a part of a vector, which contains asuitable origin of replication, and such genes encoding selectablemarkers as may be required for growth, amplification and manipulation ofthe vector, prior to its introduction into the recipient. Suitablevectors include plasmids, YACs, BACs, bacteriophage, retrovirus, and thelike. Conveniently, the expression vector will be a plasmid. Prior tovaccination, the cassette may be isolated from vector sequences bycleavage, amplification, etc. as known in the art. For injection, theDNA may be supercoiled or linear, preferably supercoiled. The cassettemay be maintained in the host cell for extended periods of time, or maybe transient, generally transient. Stable maintenance is achieved by theinclusion of sequences that provide for integration and/or maintenance,e.g. retroviral vectors, EBV vectors and the like.

The expression cassette will generally employ an exogenoustranscriptional initiation region, i.e. a promoter other than thepromoter which is associated with the T cell receptor in the normallyoccurring chromosome. The promoter is functional in host cells,particularly host cells targeted by the cassette. The promoter may beintroduced by recombinant methods in vitro, or as the result ofhomologous integration of the sequence by a suitable host cell. Thepromoter is operably linked to the coding sequence of the autoantigen toproduce a translatable mRNA transcript. Expression vectors convenientlywill have restriction sites located near the promoter sequence tofacilitate the insertion of autoantigen sequences.

Expression cassettes are prepared comprising a transcription initiationregion, which may be constitutive or inducible, the gene encoding theautoantigen sequence, and a transcriptional termination region. Theexpression cassettes may be introduced into a variety of vectors.Promoters of interest may be inducible or constitutive, usuallyconstitutive, and will provide for high levels of transcription in thevaccine recipient cells. The promoter may be active only in therecipient cell type, or may be broadly active in many different celltypes. Many strong promoters for mammalian cells are known in the art,including the β-actin promoter, SV40 early and late promoters,immunoglobulin promoter, human cytomegalovirus promoter, retroviralLTRs, etc. The promoters may or may not be associated with enhancers,where the enhancers may be naturally associated with the particularpromoter or associated with a different promoter.

A termination region is provided 3′ to the coding region, where thetermination region may be naturally associated with the variable regiondomain or may be derived from a different source. A wide variety oftermination regions may be employed without adversely affectingexpression.

The various manipulations may be carried out in vitro or may beperformed in an appropriate host, e.g. E. coli. After each manipulation,the resulting construct may be cloned, the vector isolated, and the DNAscreened or sequenced to ensure the correctness of the construct. Thesequence may be screened by restriction analysis, sequencing, or thelike.

A small number of nucleotides may be inserted at the terminus of theautoantigen sequence, usually not more than 20, more usually not morethan 15. The deletion or insertion of nucleotides will usually be as aresult of the needs of the construction, providing for convenientrestriction sites, addition of processing signals, ease of manipulation,improvement in levels of expression, or the like. In addition, one maywish to substitute one or more amino acids with a different amino acidfor similar reasons, usually not substituting more than about five aminoacids in the region.

In one embodiment of the invention the autoantigen is co-vaccinated withDNA sequences encoding a Th2 cytokine, which group includes IL-4, IL-10,TGF-β, etc. IL4 is of particular interest. The lymphokine IL-4 hasT-cell and mast cell growth factor activities. Human IL4 is an 18-kDglycoprotein. For convenience the amino acid sequence is provided hereinas SEQ ID NO:13, and the DNA sequence as SEQ ID NO:14 (Yokota et al.(1986) P.N.A.S. 83:5894–5898). This sequence is the preferred sequenceof the invention. However, the invention is not limited to the use ofthis sequence in constructs of the invention. Also of use are closelyrelated variant sequences that have the same biological activity, orsubstantially similar biological activity. A specific STAT6 DNA-bindingtarget site is found in the promoter of the IL4 receptor gene; and STAT6activates IL4 gene expression via this site. Interferons inhibitIL4-induced activation of STAT6 and STAT6-dependent gene expression, atleast in part, by inducing expression of SOCS1 (see Kotanides et al.(1996) J. Biol. Chem. 271:25555–25561).

Variant sequences encode protein subunits which, when present in a DNAconstruct of the invention, give the protein one or more of thebiological properties of IL-4 as described above. DNA sequences of theinvention may differ from a native IL-4 sequence by the deletion,insertion or substitution of one or more nucleotides, provided that theyencode a protein with the appropriate biological activity as describedabove. Similarly, they may be truncated or extended by one or morenucleotides. Alternatively, DNA sequences suitable for the practice ofthe invention may be degenerate sequences that encode the naturallyoccurring IL-4 protein. Typically, DNA sequences of the invention haveat least 70%, at least 80%, at least 90%, at least 95% or at least 99%sequence identity to a native IL-4 coding sequence. They may originatefrom any species, though DNAs encoding human proteins are preferred.Variant sequences may be prepared by any suitable means known in theart.

With respect of substitutions, conservative substitutions are preferred.Typically, conservative substitutions are substitutions in which thesubstituted amino acid is of a similar nature to the one present in thenaturally occurring protein, for example in terms of charge and/or sizeand/or polarity and/or hydrophobicity. Similarly, conservativesubstitutions typically have little or no effect on the activity of theprotein. Proteins of the invention that differ in sequence fromnaturally occurring IL-4 may be engineered to differ in activity fromnaturally occurring IL-4. Such manipulations will typically be carriedout at the nucleic acid level using recombinant techniques, as known inthe art.

The vaccine may be formulated with one or a cocktail of autoantigensequences, which may be on the same or different vectors. The DNAvectors are suspended in a physiologically acceptable buffer, generallyan aqueous solution e.g. normal saline, phosphate buffered saline,water, etc. Stabilizing agents, wetting and emulsifying agents, saltsfor varying the osmotic pressure or buffers for securing an adequate pHvalue, and skin penetration enhancers can be used as auxiliary agents.The DNA will usually be present at a concentration of at least about 1ng/ml and not more than about 10 mg/ml, usually at about from 100 μg to1 mg/ml.

In some embodiments of the present invention, the patient isadministered both an autoantigen encoding sequence and a Th2 cytokineencoding sequence. The cytokine and autoantigen can be deliveredsimultaneously, or within a short period of time, by the same or bydifferent routes. In one embodiment of the invention, the two sequencesare co-formulated, meaning that they are delivered together as part of asingle composition. The coding sequences may be associated with oneanother by covalent linkage in a single nucleic acid molecule, wherethey may be present as two distinct coding sequences separated by atranslational stop, or may be present as a single fusion protein. Thetwo sequences may also by joined by non-covalent interaction such ashydrophobic interaction, hydrogen bonding, ionic interaction, van derWaals interaction, magnetic interaction, or combinations thereof.Alternatively, the two constructs may simply be mixed in a commonsuspension, or encapsulated together in some form of delivery devicesuch as, for example, an alginate device, a liposome, chitosan vesicle,etc. (see, for example, WO 98/33520, incorporated herein by reference).

The vaccine may be fractionated into two or more doses, of at leastabout 1 μg, more usually at least about 100 μg, and preferably at leastabout 1 mg per dose, administered from about 4 days to one week apart.In some embodiments of the invention, the individual is subject to aseries of vaccinations to produce a full, broad immune response.According to this method, at least two and preferably four injectionsare given over a period of time. The period of time between injectionsmay include from 24 hours apart to two weeks or longer betweeninjections, preferably one week apart. Alternatively, at least two andup to four separate injections are given simultaneously at differentparts of the body.

The DNA vaccine is injected into muscle or other tissue subcutaneously,intradermally, intravenously, orally or directly into the spinal fluid.Of particular interest is injection into skeletal muscle. The geneticvaccine may be administered directly into the individual to be immunizedor ex vivo into removed cells of the individual which are reimplantedafter administration. By either route, the genetic material isintroduced into cells which are present in the body of the individual.Alternatively, the genetic vaccine may be introduced by various meansinto cells that are removed from the individual. Such means include, forexample, transfection, electroporation and microprojectile bombardment.After the genetic construct is taken up by the cells, they arereimplanted into the individual. Otherwise non-immunogenic cells thathave genetic constructs incorporated therein can betaken from oneindividual and implanted into another.

An example of intramuscular injection may be found in Wolff et al.(1990) Science 247:1465–1468. Jet injection may also be used forintramuscular administration, as described by Furth et al. (1992) AnalBiochem 205:365–368. The DNA may be coated onto gold microparticles, anddelivered intradermally by a particle bombardment device, or “gene gun”.Microparticle DNA vaccination has been described in the literature (see,for example, Tang et al. (1992) Nature 356:152–154). Goldmicroprojectiles are coated with the vaccine cassette, then bombardedinto skin cells.

The genetic vaccines are formulated according to the mode ofadministration to be used. One having ordinary skill in the art canreadily formulate a genetic vaccine that comprises a genetic construct.In cases where intramuscular injection is the chosen mode ofadministration, an isotonic formulation is used. Generally, additivesfor isotonicity can include sodium chloride, dextrose, mannitol,sorbitol and lactose. Isotonic solutions such as phosphate bufferedsaline are preferred. Stabilizers include gelatin and albumin.

According to the present invention, prior to or contemporaneously withadministration of the genetic construct, cells may be administered acell stimulating or cell proliferative agent, which terms are usedinterchangeably and refer to compounds that stimulate cell division andfacilitate DNA and RNA uptake.

Bupivacaine or compounds having a functional similarity may beadministered prior to or contemporaneously with the vaccine. Bupivacaineis a homologue of mepivacaine and related to lidocaine. It rendersmuscle tissue voltage sensitive to sodium challenge and effects ionconcentration within the cells. In addition to bupivacaine, mepivacaine,lidocaine and other similarly acting compounds, other contemplated cellstimulating agents include lectins, growth factors, cytokines andlymphokines such as platelet derived growth factor (PDGF), gCSF, gMCSF,epidermal growth factor (EGF) and IL4. About 50 μl to about 2 ml of 0.5%bupivacaine-HCl and 0.1% methylparaben in an isotonic pharmaceuticalcarrier may be administered to the site where the vaccine is to beadministered, preferably, 50 .mu.l to about 1500 μl, more preferablyabout 1 ml. The genetic vaccine may also be combined with collagen as anemulsion and delivered intraperatonally. The collagen emulsion providesa means for sustained release of DNA. 50 μl to 2 ml of collagen areused.

The efficiency of DNA vaccination may be improved by injection ofcardiotoxin into the tissue about one week prior to the vaccination, asdescribed by Davis et al. (1993) FEBS Lett. 333:146–150, and in theexamples. The cardiotoxin stimulates muscle degeneration andregeneration. The muscle is injected with from about 0.1 to 10 μM ofcardiotoxin dissolved in a pharmacologically acceptable vehicle.

The condition that is being treated, and the host immune status willdetermine the choice of autoantigen sequence(s). The host may beassessed for immune responsiveness to a candidate vaccine autoantigen byvarious methods known in the art.

The diagnosis may determine the level of reactivity, e.g. based on thenumber of reactive T cells found in a sample, as compared to a negativecontrol from a naive host, or standardized to a data curve obtained fromone or more patients. In addition to detecting the qualitative andquantitative presence of auto-antigen reactive T cells, the T cells maybe typed as to the expression of cytokines known to increase or suppressinflammatory responses. It may also be desirable to type the epitopicspecificity of the reactive T cells.

T cells may be isolated from patient peripheral blood, lymph nodes, orpreferably from the site inflammation. Reactivity assays may beperformed on primary T cells, or the cells may be fused to generatehybridomas. Such reactive T cells may also be used for further analysisof disease progression, by monitoring their in situ location, T cellreceptor utilization, etc. Assays for monitoring T cell responsivenessare known in the art, and include proliferation assays and cytokinerelease assays.

Proliferation assays measure the level of T cell proliferation inresponse to a specific antigen, and are widely used in the art. In anexemplary assay, patient lymph node, blood or spleen cells are obtained.A suspension of from about 10⁴ to 10⁷ cells, usually from about 10⁵ to10⁶ cells is prepared and washed, then cultured in the presence of acontrol antigen, and test antigens. The test antigens may be peptides ofany autologous antigens suspected of inducing an inflammatory T cellresponse. The cells are usually cultured for several days.Antigen-induced proliferation is assessed by the monitoring thesynthesis of DNA by the cultures, e.g. incorporation of ³H-thymidineduring the last 18 H of culture.

Enzyme linked immunosorbent assay (ELISA) assays are used to determinethe cytokine profile of reactive T cells, and may be used to monitor forthe expression of such cytokines as IL-2, IL-4, IL-5, γIFN, etc. Thecapture antibodies may be any antibody specific for a cytokine ofinterest, where supernatants from the T cell proliferation assays, asdescribed above, are conveniently used as a source of antigen. Afterblocking and washing, labeled detector antibodies are added, and theconcentrations of protein present determined as a function of the labelthat is bound.

The above diagnostic assays may be performed with various peptidesderived from the autologous protein of interest. A series of peptideshaving the sequence of an auto-antigen, e.g. PLP, MBP, etc. may be used.Possible peptides may be screened to determine which are immunodominantin the context of autoimmune disease.

The immunodominant peptides may be defined by screening with a panel ofpeptides derived from the test protein. The peptides have the amino acidsequence of a portion of the protein, usually at least about 8 and notmore than about 30 amino acids, more usually not more than about 20amino acids in length. The panel of peptides will represent the lengthof the protein sequence, i.e. all residues are present in at least onepeptide. Preferably overlapping peptides are generated, where eachpeptide is frameshifted from 1 to 5 amino acids, thereby generating amore complete set of epitopes. The peptides may be initially screened inpools, and later screened for the exact epitope to which the T cell willrespond, as previously described. Immunodominant peptides are recognizedby a significant fraction of the HLA restricted, responsive hybridomas,usually at least about 10%, more usually at least about 25%, and may beas much as 80%.

The subject therapy will desirably be administered during thepresymptomatic or preclinical stage of the disease, and in some casesduring the symptomatic stage of the disease. Early treatment ispreferable, in order to prevent the loss of function associated withinflammatory tissue damage. The presymptomatic, or preclinical stagewill be defined as that period not later than when there is T cellinvolvement at the site of disease, e.g. islets of Langerhans, synovialtissue, thyroid gland, etc., but the loss of function is not yet severeenough to produce the clinical symptoms indicative of overt disease. Tcell involvement may be evidenced by the presence of elevated numbers ofT cells at the site of disease, the presence of T cells specific forautoantigens, the release of performs and granzymes at the site ofdisease, response to immunosuppressive therapy, etc.

Degenerative joint diseases may be inflammatory, as with seronegativespondylarthropathies, e.g. ankylosing spondylitis and reactivearthritis; rheumatoid arthritis; gout; and systemic lupus erythematosus.The degenerative joint diseases have a common feature, in that thecartilage of the joint is eroded, eventually exposing the bone surface.Destruction of cartilage begins with the degradation of proteoglycan,mediated by enzymes such as stromelysin and collagenase, resulting inthe loss of the ability to resist compressive stress. Alterations in theexpression of adhesion molecules, such as CD44 (Swissprot P22511),ICAM-1 (Swissprot P05362), and extracellular matrix protein, such asfibronectin and tenascin, follow. Eventually fibrous collagens areattacked by metalloproteases, and when the collagenous microskeleton islost, repair by regeneration is impossible.

There is significant immunological activity within the synovium duringthe course of inflammatory arthritis. While treatment during earlystages is desirable, the adverse symptoms of the disease may be at leastpartially alleviated by treatment during later stages. Clinical indicesfor the severity of arthritis include pain, swelling, fatigue andmorning stiffness, and may be quantitatively monitored by Pannuscriteria. Disease progression in animal models may be followed bymeasurement of affected joint inflammation. Therapy for inflammatoryarthritis may combine the subject treatment with conventional NSAIDtreatment. Generally, the subject treatment will not be combined withsuch disease modifying drugs as cyclosporin A, methotrexate, and thelike.

A quantitative increase in myelin autoreactive T cells with the capacityto secrete IFN-gamma is associated with the pathogenesis of MS and EAE,suggesting that autoimmune inducer/helper T lymphocytes in theperipheral blood of MS patients may initiate and/or regulate thedemyelination process in patients with MS. The overt disease isassociated with muscle weakness, loss of abdominal reflexes, visualdefects and paresthesias. During the presymptomatic period there isinfiltration of leukocytes into the cerebrospinal fluid, inflammationand demyelination. Family histories and the presence of the HLAhaplotype DRB1*1501, DQA1*0102, DQB1*0602 are indicative of asusceptibility to the disease. Markers that may be monitored for diseaseprogression are the presence of antibodies in the cerebrospinal fluid,“evoked potentials” seen by electroencephalography in the visual cortexand brainstem, and the presence of spinal cord defects by MRI orcomputerized tomography. Treatment during the early stages of thedisease will slow down or arrest the further loss of neural function.

Human insulin-dependent diabetes mellitus (IDDM) is a diseasecharacterized by autoimmune destruction of the β cells in the pancreaticislets of Langerhans. An animal model for the disease is the non-obesediabetic (NOD) mouse, which develops autoimmunity. NOD micespontaneously develop inflammation of the islets and destruction of theβ cells, which leads to hyperglycemia and overt diabetes. Both CD4⁺ andCD8⁺ T cells are required for diabetes to develop: CD4⁺ T cells appearto be required for initiation of insulitis, cytokine-mediateddestruction of β cells, and probably for activation of CD8⁺ T cells. TheCD8⁺ T cells in turn mediate β cell destruction by cytotoxic effectssuch as release of granzymes, perforin, TNFα and IFNγ. Reactivities toseveral candidate autoantigens, including epitopes of insulin andglutamic acid decarboxylase (GAD), have been detected.

In one embodiment of the invention, the coding sequence used forvaccination provides for an immunogenic insulin epitope. Immunodominantepitopes include the B chain, in particular residues 9–23, which havebeen implicated in both human disease and in animal models. Epitopes ofthe pre-proinsulin have also been implicated as immunodominant epitopes.Protection from diabetes is associated with down regulation of IFN-γ andIL-10 in pancreatic lymph node cells in response to the insulin peptideencoded in the vaccine. It has been found that T cells immunized with animmunodominant insulin epitope express substantially lower levels ofIFN-γ in response to activation.

The depletion of β cells results in an inability to regulate levels ofglucose in the blood. Overt diabetes occurs when the level of glucose inthe blood rises above a specific level, usually about 250 mg/dl. Inhumans a long presymptomatic period precedes the onset of diabetes.During this period there is a gradual loss of pancreatic β cellfunction. The disease progression may be monitored in individualsdiagnosed by family history and genetic analysis as being susceptible.The most important genetic effect is seen with genes of the majorhistocompatibility locus (IDDM1), although other loci, including theinsulin gene region (IDDM2) also show linkage to the disease (see Davieset al, supra and Kennedy et al. (1995) Nature Genetics 9:293–298).

Markers that may be evaluated during the presymptomatic stage are thepresence of insulitis in the pancreas, the level and frequency of isletcell antibodies, islet cell surface antibodies, aberrant expression ofClass II MHC molecules on pancreatic β cells, glucose concentration inthe blood, and the plasma concentration of insulin. An increase in thenumber of T lymphocytes in the pancreas, islet cell antibodies and bloodglucose is indicative of the disease, as is a decrease in insulinconcentration. After the onset of overt diabetes, patients with residualb cell function, evidenced by the plasma persistence of insulinC-peptide, may also benefit from the subject treatment, to preventfurther loss of function.

Mammalian species susceptible to inflammatory conditions include caninesand felines; equines; bovines; ovines; etc. and primates, particularlyhumans. Animal models, particularly small mammals, e.g. murine,lagomorpha, etc. may be used for experimental investigations. Animalmodels of interest include those involved with the production ofantibodies having isotypes associated with IL-4 production, e.g. IgE,IgG1 and IgG4. Other uses include investigations where it is desirableto investigate a specific effect in the absence of T cell mediatedinflammation.

It is to be understood that this invention is not limited to theparticular methodology, protocols, formulations and reagents described,as such may, of course, vary. It is also to be understood that theterminology used herein is for the purpose of describing particularembodiments only, and is not intended to limit the scope of the presentinvention which will be limited only by the appended claims.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “and”, and “the” include plural referents unless thecontext clearly dictates otherwise. Thus, for example, reference to “acomplex” includes a plurality of such complexes and reference to “theformulation” includes reference to one or more formulations andequivalents thereof known to those skilled in the art, and so forth.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which this invention belongs. Although any methods, devicesand materials similar or equivalent to those described herein can beused in the practice or testing of the invention, the preferred methods,devices and materials are now described.

All publications mentioned herein are incorporated herein by referencefor the purpose of describing and disclosing, for example, the methodsand methodologies that are described in the publications which might beused in connection with the presently described invention. Thepublications discussed above and throughout the text are provided solelyfor their disclosure prior to the filing date of the presentapplication. Nothing herein is to be construed as an admission that theinventors are not entitled to antedate such disclosure by virtue ofprior invention.

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how tomake and use the subject invention, and are not intended to limit thescope of what is regarded as the invention. Efforts have been made toensure accuracy with respect to the numbers used (e.g. amounts,temperature, concentrations, etc.) but some experimental errors anddeviations should be allowed for. Unless otherwise indicated, parts areparts by weight, molecular weight is average molecular weight, andpressure is at or near atmospheric.

Experimental

Materials and Methods

Animals. Six to eight week old female SJL/J mice were purchased fromJackson Laboratory (Bar Harbor, Me.).

Antigens. Peptides were synthesized on a peptide synthesizer (model9050: MilliGen, Burlington, Mass.) by standard9-fluorenylmethoxycarbonyl chemistry. Peptides were purified by HPLC.Structure was confirmed by amino acid analysis and mass spectroscopy.Peptides used for the experiments were: PLP139–151 (SEQ ID NO:5HSLGKWLGHPDKF), PLP139–151 L144/R147 (SEQ ID NO:6 HSLGKLLGRPDKF), andPLP178–191 (SEQ ID NO:7 NTWTTCQSIAFPSK). Guinea pig spinal cordhomogenate (SCH) was used after lyophilization.

PLP peptide expression vector. Three minigenes, each one encoding a PLPepitope, were constructed by annealing two oligonucleotides with a 16mer overlapping complementary sequence (underlined), and extending withDNA polymerase and dNTPs: PLP (178–191): SEQ ID NO:8 5′-CTGGAGACCAGAATACCTGG ACCACCTGCC AGTCTATTGC CTTCCCTAGC AAGTCTAGAT AGCTA-3′ PLP(139–151): SEQ ID NO:9 5′-CTCGAGACCA TGCATTGTTT GGGAAAATGGCTAGGACATCCCGACAAGTTTTCTAGATAGCTA -3′. PLP (139–151) L144/R147 SEQ IDNO:10: 5′-CTCGAGACCATGCATTGTTTGGGAAAACTACTAGGACGCCCCGACAAGTTTTCTAGATAGCTA -3′.

These oligonucleotide duplexes were designed to incorporate Xho I andXba I restriction sites.

The products were cloned into the multiple cloning region of pTARGETVector (Promega, Madison, Wis.), a mammalian expression vector driven bythe CMV promoter. Positive clones were identified by color screening andcorrect orientation of the inserts was confirmed by DNA automaticsequencing. Purification of the plasmid DNA was done by Wizard plusMaxipreps (Promega) according to manufacturer instructions.

DNA immunization protocol. Experimental animals were injected in theleft quadriceps with 0.1 ml of 0.25% bupivacaine-HCl (Sigma, St. Louis,Mo.) in PBS. Two and ten days later, mice were injected with 0.05 ml ofplasmid DNA (1 mg/ml in PBS), in the same muscle.

ELISA for anti-PLP139–151 or anti-guinea pig SCH antibody titers.Polystyrene 96 well microtiter plates (Dynatech, Chantilly, Va.) werecoated with 0.1 ml of either peptide or guinea pig SCH, diluted in PBSat a concentration of 0.01 mg/ml in PBS. After blocking with PBS+0.5%fetal calf serum (Gibco) and 0.05% tween 20 (Bio-Rad, Hercules, Calif.),mouse sera were incubated for two hours at room temperature and antibodybinding was tested by the addition of alkaline phosphatase-conjugatedgoat anti-mouse IgG (Southern Biotechnology, Birmingham, Ala.). Afterthe addition of the enzyme substrate, plates were read at 405 nm in anELISA reader. FIG. 1 shows the results for sera taken seven days afterthe second intramuscular injection expressed as O.D. of individualsamples in a group of ten animals. O.D. values for preimmune sera were:dilution 1: 10:0.12, dilution 1:20: 0.08, and dilution 1:40: 0.03.

EAE induction. PLP139–151 peptide was dissolved in PBS to aconcentration of 2 mg/ml and emulsified with an equal volume ofIncomplete Freund's Adjuvant supplemented with 4 mg/ml heat-killedmycobacterium tuberculosis H37Ra (Difco Laboratories, Detroit, Mich.).Mice were injected subcutaneously with 0.1 ml of the peptide emulsionand, on the same day and 48 h later, intravenously with 0.1 ml of 4μg/ml Bordetella Pertussis toxin in PBS. Experimental animals werescored as follows: 0=no clinical disease; 1=tail weakness or paralysis;2=hind limb weakness; 3=hind limb paralysis; 4=forelimb weakness orparalysis; 5=moribund or dead animal.

Lymph node cell proliferation assays. Draining lymph nodes were removedfrom mice after the acute phase of disease and lymph node cells (LNC)were tested in vitro for specific proliferative responses to thePLP139–151 peptide. Cultures were prepared in flat bottom 96 wellmicrotiter plates in a volume of 0.2 ml/well at a cell concentration of2.5×10⁶/ml. The tissue culture media for the assay consisted of RPMI1640 supplemented with L-glutamine (2 mM), sodium pyruvate (1 mM), nonessential amino acids (0.1 mM), penicillin (100 U/ml), streptomycin (0.1mg/ml), 2-mercaptoethanol (5×10⁻⁵ M), and 1% autologous fresh normalmouse serum. After 72 h of incubation at 37° C., cells were pulsed for18 h with 1 μCi/well of (³H)thymidine. Plates were harvested and(³H)thymidine incorporation was measured in a scintillation counter.After recovery from the acute phase of disease animals injected eitherwith DNA coding for PLP139–151 or control vector, pTARGET weresacrified, and draining LNC were isolated. Cells were tested in vitro bystimulation with different concentrations of the peptide PLP139–151 orthe control peptide PLP178–191. Proliferative responses from pooled LNCof groups of five animals are shown in FIG. 2 as mean CPM±SD oftriplicate wells. CPM of Concanavalin A (0.001 mg/ml) stimulated LNCwere 102401 for group A and 76702 for group B.

Cytokine determination. Draining LNC (10⁷ cells/ml) from experimentalanimals were taken after the acute phase of the disease and stimulatedin vitro with varying concentrations of antigen. After 24 and 48 h ofstimulation supernatants were collected and tested by sandwich ELISA.

Ribonuclease protection assay. For mRNA detection tissue RNA samples ofLNC from experimental animals were tested using the Multi-Probe RNaseProtection Assay (RPA) System, RiboQuant (Pharmigen, San Diego, Calif.)according to manufacturer instructions.

Fluorocytometric analysis. Spleen cells (5×10⁶/ml) from naive SJL/J micewere incubated in the presence of plasmid DNA coding for the PLP139–151sequence (0.01 mg/ml) at 37° C. After 24 h cells were collected andanalyzed on FACScan flow cytometer (Becton Dickinson). The followingantibody conjugates were used: FITC anti-mouse CD80, clone 16-10A1; FITCanti-mouse CD86, clone GL1; FITC anti-mouse I-A^(k), clone 10-3.6; R-PEconjugated anti-mouse B220, clone RA3-6B2; R-PE conjugated anti-mouseCD11b, clone M1/70; PE conjugated anti-mouse, clone GK 1.5. Allantibodies were purchased from Pharmigen, San Diego, Calif. After 24 hof in vitro incubation without DNA (non) or with plasmid DNA coding forthe PLP139–151 peptide [DNA (PLP139–151)], spleen cells were stainedwith anti-Mac 1 mAb, anti-B220 mAb, anti-B7.1 mAb, and anti-B7.2 mAb asindicated. Blank refers to nonspecific background staining. Resultsshown in FIG. 4 are representative of three experiments.

Results

The minigene, coding for the PLP139–151 peptide, was cloned into anexpression vector and injected intramuscularly into SJL/J mice, twice,at one week intervals. Ten days after the last injection, experimentalanimals were bled and their sera were tested for the presence ofspecific antibodies. As shown in FIG. 1, anti-PLP139–151 IgG titers canbe detected in the mice previously injected with the PLP139–151minigene. Thus, specific serological immune responses are induced withthis particular construct.

To determine whether injection of DNA containing PLP sequences can beeffective in protecting mice from EAE induction, the PLP139–151 minigeneconstruct was injected, intramuscularly, twice, at one week intervals.Ten days after the last injection, mice were challenged with thePLP139–151 peptide emulsified in CFA. As shown in Table 1, ameliorationof acute clinical disease is observed in the animals vaccinated with thePLP139–151 plasmid vector, as compared with the control plasmid group.Onset of disease was delayed compared to the control plasmid group(11.5±0.5 days, p<0.008), mean peak disease severity was reduced(p<0.005), and mean disease score was reduced (p<0.0005). In addition,other groups were injected with either a) a plasmid containing aminigene encoding the altered peptide ligand PLP p139–151 (W144>L,H147>R), b) a plasmid containing a minigene encoding the PLP epitopep178–191. Onset of disease was delayed (11.6±0.5 days, p<0.009) and meanpeak disease score was reduced (p<0.02) with the minigene encoding thealtered peptide ligand (W144, H147). Also, onset of disease was delayed(11.5±0.4 days, p<0.003), mean peak disease severity was reduced(p<0.007), and mean disease score was reduced (p<0.0001) with theminigene encoding the PLP peptide p178–191.

TABLE 1 EAE induction in DNA immunized SJL/J mice. Mean disease Meanpeak DNA Percent score on Mean day of disease injected incidence day11^(†) disease onset severity PLP 68 (13/19)* 0.9 ± 0.3 11.5 ± 0.5 1.7 ±0.4 139-151 (p < 0.0005)^(¶) (p < 0.008) (p < 0.005) PLP 70 (14/20) 0.6± 0.2 11.5 ± 0.4 1.8 ± 0.3 178-191 (p < 0.0001) (p < 0.0035) (p < 0.007)PLP 85 (17/20) 1.2 ± 0.3 11.6 ± 0.5 2.0 ± 0.3 139-151 (p < 0.001) (p <0.009) (p < 0.01) (L > R) pTAR- 90 (18/20) 2.7 ± 0.3  10.1 ± 0.27 3.1 ±0.3 GET Non- 100 (10/10) 2.1 ± 0.7 9.9 ± 0.4 3.3 ± 0.3 plasmid *Numbersin parenthesis denotes sick animals over tested animals ^(†)Means givenas mean ± SEM. ^(¶)All p values given as comparison to pTARGET bystudent's t-test.

Mice, injected with DNA and further challenged with the encephalitogenicpeptide PLP139–151, were sacrificed after resolution of the acute phaseof the clinical disease. Draining LNC were restimulated in vitro withthe PLP139–151 peptide and tested for their proliferative responses andcytokine production. FIG. 2 shows that LNC from mice injected with DNAcoding for the PLP139–151 peptide had lower proliferative responses whencompared with the LNC from control animals (p<0.01). FIG. 3(A) showsthat, when stimulated with the PLP139–151, LNC from mice immunized withthe plasmid DNA coding for the PLP139–151 region secrete lower levels ofIL-2 and γ-interferon in comparison with control groups. In order toassess levels of cytokine mRNA transcripts in inflamed brain we utilizeda ribonuclease protection assay on mRNA isolated from brain tissue. FIG.3(B) reveals a reduction in mRNA levels of γ-interferon and IL-15 inmice immunized with the minigene encoding the PLP139–151 region.Therefore, a correlation between low incidence of clinical disease,reduced cellular responses, and low levels of IL-2, IL-15 andγ-interferon is evident in the PLP139–151 DNA vaccinated mice. Therelative expression levels of cytokine mRNA's bands shown in FIG. 3Bwere measured by densitometry. In order to correct for loadingdifferences, the values were normalized according to the level ofexpression of the housekeeping gene, GAPDH, within each sample. There isa reduction of expression level of the tested cytokines in brains ofmice vaccinated with the plasmid DNA coding for the PLP139–151determinant compared to pTARGET and PLP139–151 (L/R) plasmid DNAvaccinated mice.

In order to elucidate a mechanism for decreased T cell responses, wetested in vitro the effect of APCs, cultured in the presence of DNA, onthe proliferative responses of PLP139–151 specific T cells. Splenocyteswere incubated either with plasmid DNA coding for the PLP139–151segment, or with the PLP139–151 peptide and used as a source of APC tostimulate L139 cells, a PLP139–151 specific T cell line. Proliferativeresponses of the L139 T cell line to the above APCs were compared in thepresence or absence of anti-CD28 antibody coated beads. As shown inTable 2, L139 cells responded to syngeneic APCs preincubated with thesynthetic peptide PLP139–151 [8512 mean cpm]. This response is increasedwith addition of anti-CD28 antibodies [127281 mean cpm]. However, whenthe APCs were incubated with the plasmid DNA containing PLP139–151coding sequence, L139 cells were unable to respond to APCs [3358 meancpm], even in the presence of anti-CD28 antibodies [4532 mean cpm]. Thisdownregulation was not an effect of the plasmid itself, since APCsincubated with plasmid containing an irrelevant sequence did not affectthe proliferative response of L139 cells to anti-CD28 antibodies [4532cpm versus 26363 mean cpm, p<0.0001]. Therefore, PLP139–151 specific Tcells are unable to respond to CD28 co-stimulation when cultured in thepresence of APC loaded with plasmid DNA coding for the PLP139–151sequence.

TABLE 2 Proliferative responses of PLP139-151 specific T cells line inthe presence of syngeneic splenocytes loaded with either plasmid DNA orsynthetic peptide. pTAR- PLP139- GET 151 HSV- PLP139- Anti-CD28 plasmidplasmid VP16 151 co- CPM³ DNA¹ DNA¹ peptide¹ peptide¹ stimulation²(mean) − − − − −  2186 − − + − −  2402 − − + − +  15139 − − − + −  8512− − − + + 127281 + − − − −  2331 + − − − +  26363* − + − − −  3358 − + −− +  4532* ¹Splenocytes (5 × 10⁶/ml) from naive SJL/J mice wereirradiated (3000 rads) and incubated in the presence of either plasmidDNA coding for the PLP139-151 sequence, plasmid alone (pTARGET),PLP139-151 peptide, or control peptide (HSV VP16). Plasmid DNAconcentration was 0.01 mg/ml and peptide concentration was 0.001 mg/ml.After the initial 24 hrs of incubation splenocytes were washed twice and10,000 T cells from the PLP139-151peptide-specific T cell line, L139,were added to each well. After 48 hrs of further incubation plate waslabeled with ³H-thymidine and proliferation was assessed by harvesting18 later and counting ³H-thymidine incorporation. To demonstrate thatthe exogenously applied naked DNA is taken up by the splenocytes, and isexpressed we used reverse transcriptase-polymerase chain reaction(RT-PCR) technique. Total RNA was purified from the splenocytesusing theRneasy total RNA kit (Quiagen Inc., Valencia, CA). RT-PCR was performedusing the Access RT-PCR System (Promega Corp., Madison, WI) andoligonucleotide primers specific for the PLP139-151 minigene. Vectorspecific primers were used in a separate RT-PCR reaction to exclude thepossibility of DNA contamination. A single band corresponding to thePLP139-151 minigene was amplified from total RNA purified fromsplenocytes loaded with the PLP139-151 plasmid DNA (data not shown).²Co-stimulatory signal was delivered by adding anti-CD28 coated beads(5,000 per well) together with the T cells. Anti-CD28 antibody (clone37.51) was obtained from PharMingen (San Diego, CA). Sulfate polystyrenelatex microspheres of ~ 0.1 μm in diameter were obtained fromInterfacial Dynamics Corporation (Portland, OR). Beads (6 × 10⁶) weresuspended in 6 ml of PBS and incubated with 24 μg of anti-CD28 antibodyfor 1.5 hours at37° C. Beads were washed extensively with PBS andresuspended in RPMI-10% FCS and allowed to block for at least 30 minutesat room temperature. ³Results are expressed as mean CPM of triplicatewells. *The P value is < 0.0001 for the difference between the CPM of Tcells incubated in the presence of splenocytes with pTARGET plasmid DNAversus T cells incubated in the presence of splenocytes with PLP139-151plasmid DNA, in the presence of anti-CD28 antibodies.

The present study demonstrates protection from immunization with plasmidDNA encoding myelin minigenes. A DNA vaccine was created by insertion ofthe coding sequence for the PLP139–151 region into a bacterial plasmidunder the control of CMV promoter. This vector was injected into SJL/Jmice prior to the induction of EAE by immunization with the PLP139–151peptide in CFA. Animals receiving the plasmid coding for theencephalitogenic epitope were protected from EAE induction. Analysis ofthe immune responses in protected animals demonstrates lower T cellproliferation and decreased pro-inflammatory cytokine secretion, both inlymphoid organs and within the target organ, the brain, in comparisonwith the control group. These features suggest that DNA immunizationanergizes pathogenic T cells.

The ability of myelin minigene constructs to downregulate theco-stimulatory effect of anti-CD28 antibodies on a PLP-specific T cellline emphasizes its capacity to modulate APC-T cell interactions.Fluorocytometric analyses were carried out to determine whether DNAimmunization influences the surface expression of CD28 ligands on APCs.After 24 h of incubation with the plasmid DNA, splenocytes were stainedwith either anti-B7.1 (CD80) or anti-B7.2 (CD86) antibodies. As shown inFIG. 4, up regulation of B7.1 and B7.2 is observed in Mac-1 positivecells, but not in B220⁺ cells where downregulation of B7.2 was observed.I-A^(s) expression in spleen cells also increased in both Mac-1 and B220positive cells upon incubation with DNA.

Similar up-regulation of costimulatory molecules has been observed invivo in peripheral blood lymphocytes and spleen cells of animalsinoculated with DNA expression cassettes coding for the HIV core protein55. In contrast to this observation we found that in autoimmuneresponses to PLP139–151 the changes of expression of co-stimulatorymolecules after DNA immunization exert a protective effect by modulationof the proliferative potential and cytokine production of autoreactiveT-cells. Recently it has been reported that in EAE, there is enhancementof B7.1 expression relative to B7.2 in the splenic environment, afinding that can help explain how the immune system tilts towardautoimmunity, rather than immunological ignorance of self. InterestinglyB7.2 increases in the CNS during active EAE and during relapses.Downregulation of B7.2 correlates with remission. Changes in B7-1 andB7-2 expression upon uptake of DNA by antigen presenting cells could bea key factor in regulating T-cell responses toward self-antigens inautoimmune diseases.

DNA vaccines have been effective in generating protective immuneresponses in several models of cancer, and of viral, bacterial, andparasitic infections. Although generation of Th1-like responses may be aproperty of DNA vaccines targeting non-self antigens, Th1 responseselicited to self with DNA vaccination have not been achieved.

Biological effects of DNA motifs like unmethylated CpG dinucleotides inparticular base contexts (CpG-S motifs) may modulate innate immuneresponses when injected to animals (Krieg, A. M. et al. 1998. Trends inMicrobiol. 6, 23–27). Although we cannot discard a possible effect ofsuch sequences in the PLP139–151 and PLP139/151 (L/R) constructs, the CGmotifs in these inserts do not fulfill the complete criteria for a CpG-Smotif.

Suppression of EAE has been reported in Lewis rats by previousimmunization with DNA encoding an immunodominant MBP peptide in tandemwith IgG Fc receptor. Vaccination suppressed clinical andhistopathological signs of EAE, and reduced the interferon γ productionafter challenge with MBP 68–85 peptide [Lobell et al. (1998) J. Exp.Med. 187:1543–1548]. Vaccination was unsuccessful without inclusion ofthe tandem IgG Fc construct. In the experiments presented here, therewas apparently no need for any tandem construct in conjunction with themyelin minigene. In both the present paper and in the experimentsutilizing DNA with the Fc IgG construct, defective Th1 immunity to selfwas observed. In contrast, our laboratory has reported induction ofprotective Th2-type responses by DNA immunization in EAE [Waisman, 1996supra.]. Therefore, the immune response to a DNA vaccine encoding selfmight be very different from what is observed with DNA vaccination toforeign antigens. It might be predicted that immune responses induced byself antigens encoded in DNA vaccines will parallel what has beenobserved for immunization with the same self-antigen in peptide orprotein form. Our results suggest that a self antigen encoded in a DNAvector can anergize self-reactive T cells, and prevent an autoimmuneattack. Co-stimulation of T cells by DNA encoding self-antigens isimpaired, thus attenuating pathogenic T-cells. Our observations in theEAE suggest a model where DNA immunization can be utilized for treatmentof autoimmune disease.

EXAMPLE 2 Protection Against Autoimmune Disease with an Interleukin-4DNA Co-vaccine via Induction of T-helper 2 Cells and STAT6 Activation

The following example demonstrates that that co-vaccinating the genesfor the cytokine IL4 along with the gene for PLP₁₃₉₋₁₅₁ as two separateplasmids can provide protective immunity against EAE. In addition, amechanism is proposed, in which functional IL4 expressed from the DNAvaccine acts locally on autoreactive T cells via activation of STAT6 toshift their cytokine profile to a Th2 type. These results show theengineering of a novel method of treatment of autoimmune disease thatcombines the antigen specific effects of DNA vaccination along with thebeneficial effects of local gene delivery.

Results

The IL4 DNA vaccine produces IL4 protein. In order to construct the IL4DNA vaccine, the complete coding sequence for IL4 was amplified by PCRfrom mouse spleen cDNA. This gene was cloned into the mammalianexpression vector pTargeT under control of the CMV promoter, and theplasmid was purified as described in the methods. In order todemonstrate that the IL4 cDNA construct can indeed produce full-lengthIL4 protein, an in vitro translation system was used. When the IL4 cDNAplasmid was transcribed and translated in vitro with ³⁵S-methionine andresolved by SDS-PAGE (polyacrylamide gel electrophoresis) andautoradiography, a single product of the correct size for mouse IL4 wasseen. A control reaction with vector DNA without insert or plasmidencoding PLP₁₃₉₋₁₅₁ produced no detectable product. The predictedmolecular weight for PLP₁₃₉₋₁₅₁ is approximately 1.5 kD and, therefore,would be extremely difficult to visualize by electrophoresis.

IL4 DNA vaccination causes activation of STAT6. In order to demonstratethat a DNA vaccine can act as a gene delivery vehicle, we wanted toexplore the question of whether functional IL4 cytokine was actuallyexpressed from the DNA vaccine administered to the animal. IL4 is knownto act through the IL4 receptor to specifically activate STAT6, a memberof the signal transducers and activators of transcription family (Takedaet al. (1996) Nature 380:627–30; Quelle et al. (1995) Mol Cell Biol15:3336–43.

Mice were vaccinated intramuscularly on a once weekly basis with plasmidDNA encoding the IL4 cDNA as described in the methods. Draining lymphnodes were dissected one week after the last DNA vaccine. Proteinlysates were isolated from the lymph node cells, and probed for thepresence of activated STAT6 by Western blotting using a polyclonalantibody specific for the phosphorylated form of STAT6. As controls,mice were also vaccinated with pTargeT vector alone or with no DNA.Activated or phosphorylated STAT6 was only seen in lymph nodes from IL4DNA vaccinated mice. The phosphorylated STAT6 identified runs atapproximately 60 kD.

Identical results were obtained in a separate experiment in which micereceived three daily, rather than weekly, doses of the DNA vaccine. Micewere vaccinated intramuscularly with plasmid DNA on a daily basis forthree days. One day after the last DNA vaccine, protein lysates fromdraining lymph nodes were obtained and analyzed as above in ananti-phosphorylated STAT6 Western. A 60 kD band was seen only in thelymph node cells from IL4 DNA vaccinated mice.

Co-vaccination with DNA encoding IL4 and the PLP₁₃₉₋₁₅₁ minigeneprotects against EAE induction. In order to explore the effect ofmodifying the protection afforded by DNA immunization with the geneencoding PLP₁₃₉₋₁₅₁, we co-vaccinated mice with the genes for IL4 andPLP₁₃₉₋₁₅₁ as two separate plasmids. The murine IL4 gene was cloned intothe mammalian expression vector pTargeT under control of the CMVpromoter as described earlier. The gene encoding PLP₁₃₉₋₁₅₁ was obtainedas described above.

SJL/J mice were injected with 100 μg of each plasmid intramuscularlytwice, at one-week intervals. Control mice were injected with vectoralone or with PBS. Ten days after the last injection, the mice werechallenged for induction of EAE with the encephalitogenic peptidePLP₁₃₉₋₁₅₁ emulsified in complete Freund's adjuvant (CFA). As shown inTable 3, there is a significant decrease in the mean disease scores ofmice co-vaccinated with both the IL4 and PLP₁₃₉₋₁₅₁ plasmids compared tocontrols (see table for p values). There is also a decrease in theincidence of disease and mean peak disease severity with the co-vaccinecompared to controls. The onset of disease was not significantly delayedcompared to the control groups. No significant protection from diseasewas seen in mice vaccinated only with DNA encoding IL4.

TABLE 2 EAE disease severity in DNA vaccinated mice Mean^(a) PercentPeak Mean Mean Mean Inci- Disease Score Score Score DNA n dence Severityday 12 day 14 day 16 None 14 86 2.3 ± 0.3 1.6 ± 0.4 1.2 ± 0.2 0.7 ± 0.3pTargeT 15 93 2.4 ± 0.2 1.6 ± 0.3 1.7 ± 0.2 1.1 ± 0.2 IL4 15 80 2.7 ±0.3 1.4 ± 0.3 1.1 ± 0.2 0.4 ± 0.2 IL4 & 15 53 1.6 ± 0.3 0.8 ± 0.3 0.7 ±0.3 0.5 ± 0.2 PLP 139-151 (p < (p < (p < (p < 0.0383)^(b) 0.0494)0.0075) 0.0411) ^(a)Means given as mean ± SEM. ^(b)All p values given ascomparison of IL4/PLP139-151 to pTargeT by Student's unpaired t test.

Co-vaccination with DNA encoding IL4 rescues the T cell proliferativeresponses in PLP₁₃₉₋₁₅₁ DNA vaccinated animals. Mice that werevaccinated with DNA and challenged for disease induction with peptidePLP₁₃₉₋₁₅₁ were sacrificed after recovery from the initial acutedisease. Draining lymph node cells (LNC) were obtained from these miceand re-stimulated in vitro with the PLP₁₃₉₋₁₅₁ peptide to determinetheir proliferative responses. Furthermore, antigen specific T celllines were maintained from these LNC in order to analyze their cytokinesecretion profiles.

LNC were tested for their proliferative responses to the peptidePLP₁₃₉₋₁₅₁. There was no significant change in the proliferative patternof LNC from IL4 and PLP₁₃₉₋₁₅₁ co-DNA vaccinated mice compared tocontrol mice vaccinated with vector only. In contrast, LNC from micevaccinated only with PLP₁₃₉₋₁₅₁ DNA have a reduced proliferativecapacity. We have previously shown that these T cells are anergic(Example 1). Therefore, the addition of IL4 as a DNA co-vaccine is ableto rescue the anergy imposed by the PLP₁₃₉₋₁₅₁, DNA vaccine. Thus, adifferent mechanism of protection may be afforded by co-vaccination withIL4 DNA compared with vaccination with PLP₁₃₉₋₁₅₁ DNA alone.

Co-vaccination with DNA encoding IL4 changes the phenotype of T cellsinto a Th2 type. PLP₁₃₉₋₁₅₁ specific T cells lines were isolated andmaintained in culture from mice challenged for disease induction withthe peptide PLP₁₃₉₋₁₅₁ and previously vaccinated with variouscombinations of DNA. These T cell lines were tested for cytokineproduction after in vitro stimulation with the peptide PLP₁₃₉₋₁₅₁. Tcells from mice co-vaccinated with IL4 and PLP₁₃₉₋₁₅₁ DNA producedsignificantly higher amounts of IL4 (mean of 716±237 pg/ml vs.0.208±0.36 pg/ml from pTargeT vaccinated mice, p<0.0064) and IL10 (meanof 1073±221 pg/ml vs. 464±44 pg/ml from pTargeT vaccinated mice,p<0.0151) compared to T cells from control mice. In addition, T cellsfrom the IL4 and PLP₁₃₉₋₁₅₁ DNA co-vaccinated mice produced loweramounts of IFNγ compared to control T cells (mean of 1389±108 pg/ml vs.6689±85 pg/ml from pTargeT vaccinated mice, p<0.0001). Thus, T cellsisolated from the co-vaccinated and protected mice produce more Th2 typecytokines compared to control T cells. As reported above, T cells frommice vaccinated with PLP₁₃₉₋₁₅₁ DNA alone had a reduced amount of IFNγ,but did not undergo a Th2 shift.

Protection from EAE in IL4 and PLP₁₃₉₋₁₅₁ co-DNA vaccinated mice can betransferred by T cells. The T cells derived from mice co-vaccinated withboth IL4 DNA and PLP₁₃₉₋₁₅₁ DNA, which maintained proliferative capacitybut underwent a Th2 shift, were then tested for the capacity to transferprotection. Mice were immunized with the encephalitogenic peptidePLP₁₃₉₋₁₅₁ emulsified in CFA, and eight days later 10 million T cellswere injected intravenously into each mouse. Animals were then followedfor disease phenotype. Control T cells that are specific for PLP₁₃₉₋₁₅₁and known to induce EAE were also injected as a control. Mice injectedwith T cells derived from the co-vaccinated mice had reduced incidence(1/5 mice compare to 4/5 mice in the controls) and reduced diseasescores compared with control T cell injected mice. These resultsindicate that the protective effect achieved by IL4 and PLP₁₃₉₋₁₅₁ DNAco-vaccination can be transferred to naive animals by antigen specificTh2 cells.

Discussion

This example demonstrates a novel method of protective immunity whichcombines the effects of DNA vaccination and local gene delivery. Firstwe demonstrated that the IL4 genetic vaccine delivers functional IL4.After confirming that full-length IL4 is indeed expressed in vitro fromthe DNA construct used for the vaccination, we then showed that STAT6 isactivated in draining lymph node cells by the IL4 DNA vaccine. BecauseSTAT6 is specifically activated by IL4, we believe that the most likelyconclusion is that IL4 is produced from the DNA vaccine administered andthat it interacts with IL4 receptor on lymph node cells, which in turncauses the activation of STAT6 downstream of the receptor. Thephosphorylated STAT6 identified in the present study is approximately 60kD. Although the predominant isoform of STAT6 described in theliterature is 100 kD, other isoforms have been described in mouse immunetissues (Quelle et al., 1995). Furthermore, a recent study demonstratedthe existence of a 65 kD isoform in mouse mast cells (Sherman et al.,1999). The IL4 delivered by the DNA genetic vaccine appears tospecifically activate this isoform. We were not able to detect antibodyresponses against IL4 in the IL4 DNA vaccinated mice. Therefore, wepostulate that the IL4 gene thus delivered and expressed is effective ingenerating protective immunity without induction of an immune responseagainst IL4.

When mice were immunized with both the IL4 DNA vaccine and a separateDNA vaccine for the self-peptide PLP₁₃₉₋₁₅₁, these mice were protectedagainst induction of disease by the peptide PLP₁₃₉₋₁₅₁ emulsified inCFA. The IL4 DNA vaccine alone did not provide significant protection.When the cytokine profile of T cells from co-vaccinated and protectedmice were examined, a shift to a Th2 type of cytokine secretion patternwas seen. Furthermore, these Th2 cells could transfer protection againstdisease induction in naive mice. We thus propose that the combination ofthe local delivery of IL4 and vaccination with PLP₁₃₉₋₁₅₁ DNA causes theantigen specific autoreactive T cells to shift their phenotype to a moreprotective Th2 type of response. These antigen specific, protective Tcells are then directed to sites of myelin damage and attenuate thepathogenic autoimmune response.

A possible mechanism as to how this phenotypic shift could occur is thatthe IL4 and the PLP₁₃₉₋₁₅₁ DNA vaccines are taken up by antigenpresenting cells (APC's) at the site of administration of the vaccines.The PLP₁₃₉₋₁₅₁ peptide is expressed in the APC's and presented on MHCclass II to antigen specific T cells that are thus recruited. The APC'salso express IL4, which is secreted locally during the APC and T cellinteraction. This secreted IL4 then causes the phenotype of the antigenspecific T cell to assume a more Th2 type of phenotype. This model iscompatible with earlier studies that showed that T cells grown inculture can be caused to assume a more Th2 type of phenotype by growthin the presence of IL4 (Macatonia et al. (1993) Int Immunol 5:1119–28).

Previous studies have demonstrated that professional APC's eitherpresent at the site of administration or recruited from the bone marrowcan take up the naked DNA and travel to lymphoid organs (Chattergoon etal. (1998) J Immunol 160:5707–18). It is possible that two separate oreven distant APC's take up the two different plasmids. We believe,however, that it is the local microenvironment during the APC and T cellinteraction that is important since no detectable increase in serum IL4was seen in the IL4 DNA vaccinated mice. As a method of delivery of apotentially adverse gene product, such as a cytokine at high doses, thistechnique could be desirable over traditional gene therapy methods sincethe gene delivered acts locally rather than systemically.

DNA vaccines have proven to be effective in protecting against someanimal models of autoimmune disease. One of the many advantages of DNAvaccines over traditional treatments of autoimmune disease is theability to easily modify the treatment vehicle. We have shown here thatwith the addition of a genetically delivered IL4 cytokine to thePLP₁₃₉₋₁₅₁ DNA vaccine, we can protect against EAE and, further, drivethe protective response to a more Th2 type. The addition of IL4 as a DNAco-vaccine rescues the anergy imposed by the PLP₁₃₉₋₁₅₁ DNA vaccine, anddrives the response to a Th2 phenotype. This mechanism of protectionafforded by co-vaccination with IL4 DNA compared with vaccination withPLP₁₃₉₋₁₅₁ DNA alone, may have particular advantages. This techniquecould prove beneficial in the treatment of other autoimmune diseases.Immunization against the antigens that trigger those autoimmune diseasescaused by Th1 autoreactive cells, diseases such as multiple sclerosis,juvenile diabetes and rheumatoid arthritis, would be conditions whereco-vaccination with DNA encoding IL-4 might prove beneficial. Inconclusion, the data presented here imply a powerful and novel tool,namely the combination of local gene delivery and antigen specific DNAvaccination, that could be applied universally to all DNA vaccines.

Experimental Procedures

Animals. Six- to eight-week-old female SJL/J mice were purchased fromThe Jackson Laboratory (Bar Harbor, Me.).

Peptides. Peptides were synthesized on a peptide synthesizer (model9050; MilliGen, Burlington, Mass.) by standard9-fluorenylmethoxycarbonyl chemistry. Peptides were purified by HPLC.Structures were confirmed by amino acid analysis and mass spectroscopy.Peptides used in these experiments were: (SEQ ID NO:5) PLP₁₃₉₋₁₅₁(HSLGKWLGHPDKF) and (SEQ ID NO:15) HSVP16 P45(DMTPADALDDRDLEM).

DNA vaccines. A minigene encoding PLP₁₃₉₋₁₅₁ was constructed asdescribed above. The murine IL4 gene was cloned by PCR from spleen cDNA(Clontech, Palo Alto, Calif.) by use of the following PCR primers: (SEQID NO:16) 5′-CGCGGATCCTTGATGGGTCTCAACCCCCAGCTAGTTGTC-3′ and (SEQ ID NO:17) 5′-ACGCTCGAGGTACTACGAGTAATCCATTTGCATGATGC-3′. Both of theseconstructs were cloned into the multiple cloning region of the pTargeTvector (Promega, Madison, Wis.), driven by the CMV promoter. Correctclones were confirmed by automated DNA sequencing. Purification of theplasmid DNA was performed with the use of the Qiagen Endo-free Mega Prepkit (Qiagen, Santa Clarita, Calif.). Purity of the plasmid DNA wasconfirmed by UV spectrophotometry and agarose gel electrophoresis. OnlyDNA with a 260 nm/280 nm absorbance ratio of greater than 1.7 was used.

In vitro translation. DNA constructs used for DNA vaccination weretested for the production of the correctly sized product by an in vitrotranslation assay. Approximately 1 μg of plasmid DNA was incubated for 2hours at 30° C. in a 50 μl volume containing the following: 25 μl of TNTrabbit reticulocyte lysate (Promega Corp., Madison, Wis.), 2 μl of TNTreaction buffer (Promega Corp., Madison, Wis.), 1 μl TNT T7 RNApolymerase (Promega Corp., Madison, Wis.), 1 μl of a 1 mM amino acidmixture minus methionine (Promega Corp., Madison, Wis.), 4 μl of³⁵S-methionine at 10 mCi/ml (Amersham Life Sciences Inc., ArlingtonHeights, Ill.), and 1 μl of RNasin ribonuclease inhibitor at 40 U/μl(Promega Corp., Madison, Wis.). A 3 μl volume of the products of thisreaction was mixed with SDS-sample buffer and run on an 18% SDSpolyacrylamide gel. After drying, the gel was then exposed toautoradiography film.

STAT6 Westerns. After dissection of draining lymph nodes from DNAvaccinated mice, the tissues were mechanically homogenized in 1 ml ofthe following buffer: 0.1 M NaCl, 0.01 M Tris-HCL pH7.4, 0.001 M EDTA, 1μg/ml aprotinin, 1.6 μM Pefabloc SC (Boehringer Mannheim, Indianapolis,Ind.). 0.5 ml of the resultant lysate was used in a BCA protein assay(Pierce, Rockford, Ill.) in order to determine the total proteinconcentration. The remaining 0.5 ml was added to 0.25 ml of 3×SDSloading buffer (New England Biolabs, Beverly, Mass.) containing DTT at afinal concentration of 0.04 M. The products were resolved on a 4–15%gradient SDS-PAGE gel (Bio-Rad, Hercules, Calif.). Prestained markerswere used to determine the molecular weights (Bio Rad, Hercules,Calif.). After electrophoresis, the gels were blotted to PVDF membranes(Amersham Life Sciences Inc., Arlington Heights, Ill.) at constantvoltage of 100 V in 25 mM Tris, 192 mM glycine and 20% (v/v) methanol asthe transfer buffer. The membranes were blocked for 1 hour at roomtemperature with Tris buffered saline (TBS), 0.1% Tween 20, and 20%non-fat dry milk. After washing the membranes with TBS and 0.1% Tween20, the membranes were hybridized overnight at 4° C. with anti-phosphoSTAT6 antibody (New England Biolabs, Beverly, Mass.) diluted 1:1000 inTBS, 0.1% Tween 20, 5% BSA. The membranes were then processed as in theECL Plus protocol (Amersham Life Sciences Inc., Arlington Heights, Ill.)for visualization of the bands by chemiluminescence. The membranes werestripped by incubation in 100 mM β-mercaptoethanol, 2% (w/v) SDS, and62.5 mM Tris-HCL pH 7.4 for 30 minutes at 60° C. These same membraneswere then probed with an antibody against mouse CD3ζ (Pharmingen, SanDiego, Calif.) as a control to verify equal loading of the lanes.

DNA immunization protocol Animals were injected in the left quadricepswith 0.1 ml of 0.25% bupivicaine-HCL (Sigma, St. Louis, Mo.) in PBS. Twoand 9 days later, mice were injected with 100 μg of plasmid DNA (at aconcentration of 1 mg/ml in PBS) in the same muscle. Animals receiving aco-vaccine received two separate injections of each plasmid DNA.

EAE induction. Seven to 10 days after the final DNA vaccine, EAE wasinduced in mice with 100 μg of PLP₁₃₉₋₁₅₁ peptide. The peptide wasdissolved in PBS at a concentration of 2 mg/ml and emulsified with anequal volume of incomplete Freund's adjuvant supplemented with 4 mg/mlheat killed mycobacterium tuberculosis H37Ra (Difco Laboratories,Detroit, Mich.). Mice were injected subcutaneously with 0.1 ml of thepeptide emulsion. Experimental animals were scored as follows: 1, tailweakness or paralysis; 2, hind limb weakness; 3, hind limb paralysis; 4,forelimb weakness or paralysis; and 5, moribund or dead animals.

Lymph node cell proliferation assays. After the acute phase of disease,draining lymph nodes were dissected and lymph node cells (LNC) werecultured in vitro for specific proliferative response to the PLP₁₃₉₋₁₅₁peptide. LNC's were prepared in 96-well microtiter plates in a volume of0.2 ml/well at a concentration of 2.5×10⁶ cells/ml. The culture mediumconsisted of enriched RPMI (RPMI 1640 supplemented with L-glutamine [2mM], sodium pyruvate [1 mM], nonessential amino acids [0.1 mM],penicillin [100 U/ml], streptomycin [0.1 mg/ml], 2-ME [5×10⁻⁵ M])supplemented with 1% autologous fresh normal mouse serum. Cultures wereincubated at 37° C. and after 72 hours, cells were pulsed for 18 hourswith 1 μCi/well of [³H]thymidine. The cells were then harvested andcounted in a beta counter.

Cytokine profile determination. T cell lines were established from LNC'sderived from DNA vaccinated mice. These T cells were then tested for theproduction of various cytokines. 50×10³ T cells/ml were incubated with2.5×10⁶ irradiated syngenic APC's/ml in enriched RPMI and 10% FCS. After6 days of culture the supernatants were collected and tested by sandwichELISA using standard ELISA kits (Pharmingen, San Diego, Calif.).

EXAMPLE 3 Immunization with DNA Encoding an Immunodominant Peptide ofInsulin Prevents Diabetes in NOD Mice

The NOD mouse is an animal model of IDDM in which several autoantigens,including insulin, have been identified. In this study it is proven thatvaccination of NOD mice with DNA encoding an immunodominant peptide ofinsulin protects the animals from developing diabetes. These resultsconfirm that DNA vaccination has a protective effect on autoimmunity andopens doors for novel therapies.

Materials and Methods

Animals. Three- to four-week-old female NOD mice were purchased fromTaconic Farms (Germantown, N.Y.) and maintained in the Department ofComparative Medicine at Stanford University.

Mice were tested weekly for glucosuria by Chemstrip (Boehringer MannheimCo., Indianapolis, Ind.), and diabetes was confirmed by plasma glucosemeasurement using the One Touch II meter (Johnson & Johnson, Milpitas,Calif.). Animals having repeated plasma glucose levels greater than 250mg/dl were considered diabetic.

Insulin peptide expression vectors. Overlapping sense and antisenseoligonucleotide sequences encoding the A(7–21) and B(9–23) peptides ofinsulin were synthesized by the PAN facility at Stanford UniversityMedical Center. The nucleotide sequence of the insulin A (+) strand is(SEQ ID NO:18) 5′ CCGGAATTCGCCATGTGCACGTCAATCTGTTCACTGTACCAGCTAGAGAACTACTGCAACTAGTCTAQGAGC-3′; the sequence of the insulin B (+)strand is (SEQ ID NO:19) 5′-CCGGAATTCGCCATGAGCCACCTAGTAGAAGCACTAACCTCGTATGCGGCGAACGAGGTTAGTCTAGAGC-3′. These were designed to incorporateEcoRI and XbaI restriction sites for cloning. The products were clonedinto the multiple cloning region of PcDNA3.1⁺ expression vector(Invitrogen, Carlsbad, Calif.). Purification of the plasmid DNA wascarried out using Qiagen Endo-free Mega-prep kits (Qiagen, Valencia,Calif.).

Protein and peptides. Whole porcine insulin was purchased from Sigma(St. Louis, Mo.). Insulin peptides were synthesized and HPLC purified bythe PAN facility at Stanford University. The amino acid sequence of theinsulin A (7–21) peptide is (SEQ ID NO:20) CTSICSLYQLENYCN; the sequenceof insulin B (9–23) is (SEQ ID NO:21) SHLVEALYLVCGERG. The controlpeptide “p43” is derived from Bacillus subtilis hyp protein X13 and hasthe sequence (SEQ ID NO:22) RKVVTDFFKNIPQRI.

DNA Immunization Protocol. Experimental animals were injected at 3 to 4weeks of age in the quadricep with 0.1 ml of 0.25% bupivicaine-HCL(Sigma, St. Louis, Mo.) in PBS (0.05 ml per quadricep). Two daysfollowing, mice were injected with 0.05 ml of plasmid DNA at 1.0 mg/mlin each quadricep. The plasmid DNA was injected two more times atten-day intervals.

Histology. The pancreata were removed from experimental and controlanimals, fixed in 10% formaldehyde, and embedded in paraffin. Thinsections at three levels, 50 μm apart, were cut for staining withhematoxylin and eosin. The severity of infiltration was assessed bylight microscopy. Three and five animals from each group were analyzedfor two individual experiments, respectively. At least 25 islets wereexamined per pancreas.

Proliferation Assays. Ten days after the third injection of plasmid DNA,animals were sacrificed and their splenocytes tested in vitro forproliferative responses to insulin peptides and to other islet antigenpeptides. A non-relevant peptide p43 was used as a control. Cells wereplated in flat-bottom 96-well microtiter plates in a volume of 0.2 mlper well at a concentration of 2.5×10⁶ cells per ml. Tissue culturemedia for the assay consisted of RPMI 1640 supplemented with L-glutamine(2 mM), sodium pyruvate (1 mM) nonessential amino acids (0.1 mM),penicillin (100 U/ml), streptomycin (0.1 mg/ml), 2-ME (5×10⁻⁵ M), and 1%autologous fresh normal mouse serum. After 72 hours of incubation at 37° C., cells were pulsed with 1 μCi/well of [³H]thymidine for anadditional 18 hours. Plates were harvested and [³H] thymidineincorporation was measured in a scintillation counter.

Serum Antibody ELISAs. Polystyrene 96-well microtiter plates were coatedwith 100 μl peptide or protein at a concentration of 10 μg/ml in PBS.Plates were washed and blocked with PBS containing 5% FCS for 1 hour atroom temperature. Diluted serum samples from vaccinated or non-treatedanimals was added and incubated overnight at 4° C. After washing, goatanti-mouse IgG conjugated to alkaline phosphatase (SouthernBiotechnology Associates, Birmingham, Ala.) was added, and platesincubated for 1 hour at 37° C. After addition of the enzyme substrate,plates were read at 405 nm in an ELISA reader.

Real Time Quantitative PCR analysis of cytokine mRNA. Five days afterthe second injection, pancreatic lymph nodes were harvested and singlecell suspension prepared. Ten million cells from each group were platedin 1.5 mL final volume with 10 μg/mL insulin B peptide. After 72 hourscells were collected and pelleted for RNA extraction using the RNeasykit (Quiagen, Valencia, Calif.). The RNA was treated with DNase toremove all genomic DNA and reverse transcribed with MultiScribe reversetranscriptase (PE Applied Biosystems, Foster City, Calif.) in thepresence of hexamers, according to manufacturer's instructions.

Real time quantitative PCR was carried out for IL-4, IFN-γ, IL-10,TGF-β, and ribosomal RNA (internal control) in the ABI Prism 7700sequence detector, which contains a GeneAmp PCR system R600 (PE AppliedBiosystems). The probes were labeled with the fluorescent reporter dyeFAM (6-carboxyfluorescein, covalently linked to the 5′ end of theoligonucleotide) and a quencher, TAMRA. The primer and probe sequencesused were the following: (SEQ ID NO:23) 5′ IL-4 primer, CATCGGCATTTTGAA;(SEQ ID NO:24) 3′ IL-4 primer, CGTTTGGCACATCCATCTCC; IL-4 probe, (SEQ IDNO:25) CACAGGAGAAGGGACGCCATGCA; 5′ IFN-γ primer, (SEQ ID NO:26)TCCTGCGGCCTAGCTCTGA; 3′ IFN-γ primer, (SEQ ID NO:27) GCCATGAGGAAGAGCT;IFN-γ probe, (SEQ ID NO:28) ACAATGAACGCTACACACTGCATCTTGGC; 5′ IL-10primer, (SEQ ID NO:29) TGCAGCAGCTCAGAGGGTTC; 3′ IL-10 primer, (SEQ IDNO:30) CTGGCCACAGTTTTCAGGGA; IL-10 probe, (SEQ ID NO:31)CCTACTGTCATCCCCCAGCCGCTTC; 5′ TGF-β primer, (SEQ ID NO:32)GCAACATGTGGAACTCTACCAGAA; 3′ TGF-β primer, (SEQ ID NO:33)GACGTCAAAAGACAGCCACTC; TGF-β probe, (SEQ ID NO:34)ACCTTGGTAACCGGCTGCTGACCC. All reactions were performed using the TaqManGold PT-PCR kit according to the manufacturer's instructions (PE AppliedBiosystems). For the different runs cDNA corresponding to 5 ng of totalRNA was used. A normalization to ribosomal RNA was performed for eachsample.

Statistical analysis. Disease was compared using an Analysis of MaximumLikelihood Estimate and incidence rate. Proliferation measurements werecompared using an F-ratio and student's t-test.

Results

NOD mice immunized with plasmid encoding the insulin B chain peptide9–23 are protected from diabetes. To test the efficacy of an insulin DNAvaccine in the NOD mouse model, groups of 10, 4-week-old NOD mice wereinjected with the DNA vaccine constructs and monitored for diabetesweekly, as determined by glucosuria and hyperglycemia, for >30 weeks.Results represent two independent experiments. Animals were monitoredfor glucosuria twice weekly. Diabetes was established by two consecutivereadings >250 mg/dl, and confirmed by blood glucose measurement. Datashown represents 10+10 mice studied over two experiments.

In the untreated and plasmid control (PcDNA) injected groups, 70% of themice developed diabetes by 34 weeks of age (FIG. 5). In the insB-PcDNAinjected group, however, only 20% developed diabetes by the same age(p=0.02 by X² analysis). Furthermore, the onset of disease was markedlydelayed in this group as well, from <14 weeks for the first animal tobecome diabetic in the untreated group, to >17 weeks for the insB-PcDNAvaccinated group. The diabetes incidence rate for the PcDNA anduntreated control groups was 3 times the rate for the insB-PcDNA group(0.035 and 0.036 for the PcDNA and untreated groups, respectively,compared to 0.012 for insB-PcDNA group.)

In InsB-PcDNA vaccinated NOD mice, insulitis coexists with protection.Pancreata were removed from immunized and control animals at 7 weeks ofage, a time at which the initial infiltration of some islets is clearlyvisible by histological staining of NOD pancreata. A minimum oftwenty-five islets each for five animals per group were scored forinsulitis. Staining of pancreata from older (16-week-old) mice yieldedsimilar results. Although animals injected with insulin DNA showed noclinical signs of diabetes, islet infiltration (insulitis) was visibleat levels comparable to that seen in the control animals. Hencevaccination with insulin DNA did not affect gross trafficking oflymphocytes to the islets of Langerhans.

Proliferative responses of InsB-PcDNA Vaccinated NOD splenocytes againstinsulin are unaltered compared to controls. Spleens were harvested fromimmunized animals 10 days following the third immunization and testedfor proliferative responses against insulin. We found a modest but notsignificant increase in proliferation by InsB-PcDNA immunizedsplenocytes compared to controls, which may reflect priming of the smallpopulation of insulin-specific cells. Nonetheless, these resultsindicate that the mechanism of protection from IDDM is not dependent oninduction of anergy in insulin-specific cells.

Insulin-specific antibodies are not induced by InsB-PcDNA vaccination.We tested whether DNA immunization induced antibodies against theinsulin peptide, or against other NOD autoantigens. Mice were bled atearly (8 weeks) and late (25 weeks) time points, and the serum tested byELISA for antibodies against whole insulin, insulin B (9–23), insulin A(7–21), GAD65, and Hsp60. We found no differences between groups inantibody levels against the insulin B peptide, nor against any of theother candidate antigens.

Immunization with Insulin B (9–23) DNA induces an antigen-specificresponse in the pancreatic lymph nodes. In order to detectantigen-specific responses in vitro, we used quantitative PCR to assesslevels of cytokine mRNA production (FIG. 6). Pancreatic lymph node cellsfrom NOD mice vaccinated twice at a ten day interval with either PcDNAor InsB-PcDNA were harvested 5 days after the second injection. Cellswere cultured in the presence of insulin B (9–23) peptide for 72 hours,then pelleted for quantitative PCR analysis of cytokine mRNA levels.

In three independent experiments, groups of animals were injected twicewith either the insB-PcDNA or the PcDNA control plasmid. Five days afterthe second injection, pancreatic lymph nodes were harvested andsingle-cell suspension plated with 10 μg/mL insulin B (9–23) peptide.After 72 hours the cells were pelleted, and subjected to quantitativePCR analysis for IL-4, TGF-β, IL-10, and IFN-γ message levels.Quantitative PCR comparison of cytokine message levels in pancreaticlymph node cells showed a significant reduction in IFN-γ and IL-10levels in the insB-PcDNA vaccinated animals compared to PcDNA-vaccinatedcontrols. IFN-γ levels from insB-PcDNA-vaccinated lymph nodes were 38%that of PcDNA vaccinated lymph nodes (p<0.05) in response to insulin Bpeptide stimulation. Furthermore, IL-10 levels in InsB-PcDNA vaccinatedmice were 30% of PcDNA control levels (p<0.01). Changes in mRNA levelsof IL-4 and TGF-β were not significant over the three experiments.

The above data demonstrate the successful vaccination of NOD mice withinsulin B (9–23) DNA to confer protection from diabetes. The effect isspecific to DNA encoding immunogenic insulin, since empty plasmid alone,or DNA encoding a non-immunogenic peptide of insulin, did not have asignificant effect on disease. Bacterial CpG motifs could not accountfor the protection, since the plasmid encoding insulin A (7–21), whichwas identical in length and contained the same number of CpGs, did notalter disease incidence significantly. Disease onset was substantiallydelayed in the InsB-PcDNA vaccinated mice that did become diabetic,reiterating the protective potential of DNA vaccination. Protection fromdiabetes appeared to be associated with down regulation of IFN-γ andIL-10 in pancreatic lymph node cells in response to the insulin Bpeptide encoded in the vaccine.

Insulitis was not abolished in protected animals, indicating that DNAvaccination did not reduce the gross trafficking of cells to the islets,although there may be a selective alteration in lymphocyte trafficking.Furthermore, the infiltrate was relatively non-destructive within thetime of analysis (up to 16 weeks of age), as most InsB-PcDNA vaccinatedmice did not become diabetic. This outcome is consistent with datadescribing polypeptide based immunization with whole insulin or with theB chain peptide. Regulation of diabetes does not necessarily take placeat the level of infiltration of the islets by lymphocytes, but rather,at the level of the actual destruction of the insulin-secreting β cells.

There was no significant increase in T cell proliferative responses toinsulin B peptide and whole insulin by splenocytes of insB-PcDNAvaccinated animals. This result indicates that insulin B (9–23) DNAvaccination in the NOD mice does not anergize or eliminate T cellsspecific for the encoded peptide. Rather, it was found that cells frominsB-PcDNA immunized animals expressed substantially lower amounts ofIFN-γ than did cells from control vaccinated animals. This downregulation of IFN-γ secretion in response to activation correlatesstrongly with protection from diabetes, since IFN-γ is known to be acritical mediator of inflammation of the islets and of β celldestruction. The decrease in levels of IL-10 expression may alsocontribute to protection from disease.

These results suggest that DNA vaccination may be an effective method ofaltering harmful immune responses in autoimmunity to confer protection.Furthermore, DNA vaccination will be a powerful tool in modulatingdisease.

1. A method for reducing disease severity in a human afflicted with multiple sclerosis comprising administering intramuscularly to the subject a plasmid DNA vector having a low number of CpG motifs compared to the unmodified plasmid DNA vector and comprising an expression cassette, the expression cassette comprising a DNA encoding at least one immunodominant epitope of a human autoantigen associated with multiple sclerosis, so as to thereby reduce disease severity in the subject.
 2. The method of claim 1, wherein the autoantigen is a polypeptide.
 3. The method of claim 1, wherein the autoantigen is a peptide.
 4. The method of claim 1, wherein the autoantigen is a proteolipid protein.
 5. The method of claim 1, wherein the autoantigen is a myelin-oligodendrocyte glycoprotein.
 6. The method of claim 1, wherein the autoantigen is a myelin-associated glycoprotein.
 7. The method of claim 1, wherein the autoantigen is a myelin basic protein. 